arXiv 1910.144042019-10nucl-exhep-ex

$\sqrt{s_{\rm NN}}$ = 5.02 TeV时Pb-Pb碰撞中快度J/ $ψ$产生的中心性和横向动量依赖性

Centrality and transverse momentum dependence of inclusive J/$ψ$ production at midrapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

ALICE Collaboration

备注：: 24 pages, 8 captioned figures, 2 tables, authors from page 19, published version, figures at http://alice-publications.web.cern.ch/node/5653
发表信息：: PLB 805 (2020) 135434
DOI：: 10.1016/j.physletb.2020.135434

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摘要：

ALICE合作组报道了在中快度（$|y|$ < 0.9）时，每个核子-核子碰撞的质心能量为$\sqrt{s_{\rm NN}}$ = 5.02 TeV的Pb-Pb碰撞中J/ $ψ$介子的产生.测量是在双电子衰变通道中进行的，作为事件中心性和J/ $ψ$横向动量$p_{\rm T}$的函数，下降到$p_{\rm T}$ = 0 GeV/ $c$。计算J/ $ψ$平均横向动量$\langle p_{\rm T} \rangle$和$r_{\rm AA}$比（定义为$\langle p^{\rm 2}_{\rm T} \rangle_{\rm PbPb}/\langle p^{\rm 2}_{\rm T} \rangle_{\rm pp}$）。这两个观测值都显示出对中心（正面）碰撞的中心性依赖性。J/ $ψ$核修饰因子$R_{\rm AA}$表现出强烈的$p_{\rm T}$依赖性，在高$p_{\rm T}$时具有较大的抑制，在降低$p_{\rm T}$时增加至1。当在测量的动量范围$p_{\rm T}$ < 10 GeV/ $c$上积分时，J/ $ψ$ $R_{\rm AA}$表现出弱的中心依赖性。每个测量结果进行比较，在较低的质量中心的能量和ALICE测量在前进的快度，以及理论计算。在低$p_{\rm T}$下J/ $ψ$产生的所有报告特征与源自粲夸克（再）组合对J/ $ψ$产额的主要贡献一致。

英文摘要：

The inclusive J/$ψ$ meson production in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision of $\sqrt{s_{\rm NN}}$ = 5.02 TeV at midrapidity ($|y|$ < 0.9) is reported by the ALICE Collaboration. The measurements are performed in the dielectron decay channel, as a function of event centrality and J/$ψ$ transverse momentum $p_{\rm T}$, down to $p_{\rm T}$ = 0 GeV/$c$. The J/$ψ$ mean transverse momentum $\langle p_{\rm T} \rangle$ and $r_{\rm AA}$ ratio, defined as $\langle p^{\rm 2}_{\rm T} \rangle_{\rm PbPb}/\langle p^{\rm 2}_{\rm T} \rangle_{\rm pp}$, are evaluated. Both observables show a centrality dependence decreasing towards central (head-on) collisions. The J/$ψ$ nuclear modification factor $R_{\rm AA}$ exhibits a strong $p_{\rm T}$ dependence with a large suppression at high $p_{\rm T}$ and an increase to unity for decreasing $p_{\rm T}$. When integrating over the measured momentum range $p_{\rm T}$ < 10 GeV/$c$, the J/$ψ$ $R_{\rm AA}$ shows a weak centrality dependence. Each measurement is compared with results at lower center-of-mass energies and with ALICE measurements at forward rapidity, as well as to theory calculations. All reported features of the J/$ψ$ production at low $p_{\rm T}$ are consistent with a dominant contribution to the J/$ψ$ yield originating from charm quark (re)combination.

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